Buffers Evaluation Information Page

Broad definition of what we are considering

We primarily considered videos focused on conceptual understanding of buffer systems. This includes how buffers are formed, how buffers work, what limits the capacity of buffers, why buffers are useful. We did not focus on videos that exclusively solve mathematical problems involving buffers without addressing the conceptual aspects. Note, videos that only use Henderson-Hasselbalch equation to solve buffer problem CANNOT meet concept of interest.

Johnstone's Triangle Elements

Acids and Bases Specific Criteria

Element	Examples
Macroscopic	Examples of buffer solutions in everyday life (e.g., blood, ocean water). Needs to actually include what the buffer system is. Demonstrations of how buffers resist changes in pH when acids or bases are added. Acid base indicator and color changes. Note: many physiological examples (e.g., blood maintaining pH are verbal only as it is really hard to show this visually)
Symbolic	Chemical equations showing the components of a buffer (e.g., weak acid and its conjugate base). Graphs or diagrams illustrating buffer capacity and pH changes. Equations involving buffer systems (e.g., Henderson-Hasselbalch equation).
Particulate	Particle diagrams showing the interactions between buffer components and added acids or bases. Illustrations of how buffer components neutralize added H⁺ or OH^- ions at the particulate level, though this must show more than one H⁺ or OH^- ion reacting.
Connection between levels	Videos should make explicit connections between two or more levels for this to be coded as present. For example, they could show a macroscopic example of a buffer solution resisting pH changes and connect it to particle diagrams showing neutralization and symbolic representations of buffer equations.

Core Ideas

Change and Stability in Chemical Systems	Atomic/Molecular Structure & Properties	Electrostatic Bonding and Interactions
Core Ideas Elements
Energy and entropy changes, the rates of competing processes, and the balance between opposing forces govern the fate of chemical systems.	The macroscopic physical and chemical properties of a substance are determined by the three‐dimensional structure, the distribution of electron density, and the nature and extent of noncovalent interactions between the particles.	Attractive and repulsive electrostatic forces govern noncovalent and bonding (covalent and ionic) interactions between atoms and molecules. The strength of these forces depends on the magnitude of the charges involved and the distances between them.
Video needs to include: Buffers are equilibrium systems comprised of a weak acid and its conjugate base (or weak base and its conjugate acid). They resist changes in pH when small amounts of strong acids or bases are added through a chemical reaction that shifts the equilibrium position slightly. OR Buffers are equilibrium systems comprised of a weak acid and its conjugate base (or weak base and its conjugate acid). They keep the H⁺ ion concentration constant by shifting the equilibrium system to adjust for added or lost H⁺.	Video needs to include: Buffers work through reactions between components of the buffer equilibrium system (acid or base) and the added H+or OH-. If either buffer component is used up, the buffer will no longer work (buffer capacity will be exceeded).	Video needs to include: A buffer requires both the acid and the base to have significant ability to react. Further, because the components must not react together to neutralize each other, only weak conjugate acid/base pairs form buffers. Alternately, videos may address at the molecular structure level why strong acids/bases and their conjugate can not form buffers. The idea must be linked to the structural features of the compounds, not simply stated as a definition.

Casual Mechanistic Reasoning

Must have both How and Why?

Option 1: What causes a buffer to resist changes in pH? How: Buffers resist changes in pH (or keeping H⁺ concentration constant) through neutralization reactions between the buffer components (weak acid and conjugate base or weak base and conjugate acid) and added acids or bases. Why: The conjugate acid/base pair are in equilibrium with each other in the buffer system. Any added H⁺ or OH^– will react with components of that equilibrium system and cause a shift in the equilibrium position rather than having significant changes in the concentration of H⁺ or OH^– To meet this causal mechansitic reasoning criteria, the video must acknolwedge that there is an equilibrium present.

Option 2: What makes a good or poor buffer?

How: An acid/conjugate base system that is in equilibrium is required for a buffer.

Why: This dynamic equilibrium between the weak acid and its conjugate base allows the buffer to neutralize added acids or bases, maintaining a stable pH. A system of a strong acid and its conjugate base will neutralize added base; however, the conjugate base of a strong acid is stable and thus will not react appreciably with added acid to neutralize it. (And the analogous case for a strong base and conjugate acid).

Option 3: What causes a buffer to break down?

How: Buffer capacity is influenced by the concentration of the weak acid and its conjugate base (or weak base and conjugate acid). Higher concentrations of buffer components result in greater capacity to neutralize added acids or bases.

Why: With higher concentrations, there are more base/acid molecules available to react with added H⁺ or OH^–– ions, enhancing the buffer’s ability to resist pH changes. If there are no more base/acid molecules to react with the added H⁺ or OH^– ions, the buffer will no longer work.

Scientific Practices

Most Frequent Science Practices
SP 2: Developing and Using Models Instruction presents an event, observation, or phenomenon for instructor/students to explain or make a prediction about. Instruction presents a representation or asks instructor/students to construct a representation. Instruction has instructor/students explain or make a prediction about the event, observation, or phenomenon. Instruction has instructor/students provide the reasoning that links the representation to their explanation or prediction.
SP 4: Analyzing and Interpreting Data Instruction presents a scientific question, claim, or hypothesis to be investigated. Instruction provides a representation of data (table, graph, or list of observations) used to answer the question or test the claim or hypothesis. Instruction provides an analysis of the data or asks instructor/students to analyze the data. Instruction has instructor/students interpret the results or assess the validity of the conclusions in the context of the scientific question, claim, or hypothesis.
SP 5: Using Mathematics and Computational Thinking Instruction presents an event, observation, or phenomenon. Instruction has instructor/students perform a calculation or statistical test, generate a mathematical representation, or demonstrate a relationship between parameters. Instruction has instructor/students give a consequence or an interpretation in words, diagrams, symbols, or graphs of their mathematical results while demonstrating reasoning in the context of the given event, observation, or phenomenon.
SP 6: Constructing Explanations and Engaging in Argument from Evidence Instruction presents an event, observation, or phenomenon. Instruction presents or asks instructor/students to make a claim based on the given event, observation, or phenomenon. Instruction has instructor/students provide scientific principles or evidence (data or observations) to support the claim. Instruction has instructor/students provide reasoning about why the scientific principles or evidence support the claim.

Multimedia Principles

Multimedia learning as knowledge construction: The goal of multimedia presentations is not only to present information but also to provide guidance for how to process the presented information – that is, for determining what to pay attention to, how to mentally organize it, and how to relate it to prior knowledge. We will categorize the videos along each of the following criteria (High and Low should be mutually exclusive.)

High	Low
Video almost exclusively involves meaningful and relevant images and verbal components AND images are explained for a novice learner Text on screen is minimal (ex. Only brief bullet points or keywords or definitions if text is used) Content is all relevant to the topic and learning (no music, unhelpful animations, graphics, etc.) Contains elements that meaningfully support student organizing content or identify key ideas (introductory organizer, section heading, summary, guiding questions/topic (for short, focused video only) Key Question: Could a novice learner clearly understand what they should take away from the video? Yes=high.	Large segments of video are presented just verbally and not pictorially (ex. just the instructor talking, or just written words) OR images presented are not relevant to learning or explained Contains full sentences of written text that are also narrated (e.g., several bullet points or sentences on one screen OR full sentences of text on many screens includes forced closed captioning) Contains extraneous content, music, graphics, animations, background changes, sounds, or just too much stuff on the screen at one time - anything that detracts attention from core content Does not contain any elements that meaningfully help learners organize content or identify key ideas (e.g., no introductory organizer, section headings, video segments, summary, guiding question/topic (for short focused videos only)

High

Low

Video almost exclusively involves meaningful
and relevant images and verbal components
AND images are explained for a novice
learner
Text on screen is minimal (ex. Only brief
bullet points or keywords or definitions if text
is used)
Content is all relevant to the topic and learning
(no music, unhelpful animations, graphics,
etc.)
Contains elements that meaningfully support
student organizing content or identify key
ideas (introductory organizer, section heading,
summary, guiding questions/topic (for short,
focused video only) Key Question: Could a
novice learner clearly understand what they
should take away from the video? Yes=high.

Large segments of video are presented just
verbally and not pictorially (ex. just the
instructor talking, or just written words) OR
images presented are not relevant to learning
or explained
Contains full sentences of written text that are
also narrated (e.g., several bullet points or
sentences on one screen OR full sentences of
text on many screens includes forced closed
captioning)
Contains extraneous content, music, graphics,
animations, background changes, sounds, or
just too much stuff on the screen at one time -
anything that detracts attention from core
content
Does not contain any elements that
meaningfully help learners organize content or
identify key ideas (e.g., no introductory
organizer, section headings, video segments,
summary, guiding question/topic (for short
focused videos only)

Misleading vs. Inaccuracies

Several minor spelling issues is misleading, not inaccurate

Example High Quality Videos

Examplar Videos

These are examples of videos that were found to provide good illustrations of some or many of the framework components for this concept. Develop a deep understanding of chemistry concepts requires multiple experiences with the material and these videos may provide one such experience.

Exemplar Video 1	Exemplar Video 2
Strengths This video is high in pretty much everything. Video is split into two parts. The first part addresses how a buffer works starting with a macroscopic example and then goes through the development of a model using lego pieces to explain the macroscopic observations. The model development is particularly well done highlighting the observations that the model needs to explain and makes adjustments to the model when there are observations that it does not explain. Part 2 addresses the design of a buffer, starting with why you would want to make a buffer and highlighting the buffer system in blood. Again through model building and revision determines that a buffer must consist of a WA and its CB (or vice versa) AND addresses the idea of buffer capacity - you need enough of each component present to have an effect.	Strengths This video does a really nice job of grounding the concept of buffers in a phenomena (Clark Fork River). Uses a similare model and calculations to explain how a buffer works, and then ties back to the real world, more complext example.
Weaknesses The only weakness is its length. It is 17:28 which is longer than our typical videos, but is one of the best videos we have seen.	Weaknesses There are some side stories and many transitions between narrator, content slides, and demonstrations that could be distracting for novice learner. Also does not include particle representations to support student conceptual understanding at the particle level.

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